Method of making electrical contact elements



Patented Mar. 22, 1949 METHOD OF MAKING ELECTRICAL CONTACT ELEMENTS Roy L. Adams and Lyall Zickrick, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York N Drawing.

Original application October 8,

1943, Serial No. 505,536. Divided and this application August 3, 1945, Serial No. 608,832

1 Claim. 1

Our invention relates to method of making contact elements and particularly to such elements as are used with electrical apparatus as current collecting brushes.

This application is a division of our copending application Serial Number 505,536, filed October 8, 1943, and assigned to the assignee of this application which has become Patent No. 2,418,811.

An object of our invention is to provide an improved method of making electrical contact element.

A further object of our invention is to provide an improved method of making electric current collector contact element including a carbonaceous material and provided with an inorganic lubricant for the contact surface thereof.

Further objects and advantages of our invention will become apparent and our invention will be better understood from the following description, and the features of novelty which characterize our invention will be pointed out in the claims annexed to and forming a part of this specification.

It ha been found that under normal atmospheric conditions with average humidity atmospheric water vapor and oxygen together provide one of the best known lubricants for the contact surfaces of carbon and metal-graphite brushes and similar bearing surfaces. It also has been found that electrical contact elements made of porous blocks of finely divided electrically conductive material such as carbon or metal-graphite brushes tend to wear away very rapidly in dry or rarefied atmospheres.

We have found that a relatively movable contact element such as might be used for an electrical brush contact or a relatively movable bearing element for contact with another member, such as a rotating slip ring or commutator, will have a relatively long wearing life when it is made of a graphitic or carbonaceous material intimately combined with a metal and sulphur. Different proportions of these ingredients have been found to be useful for different operating conditions in connection with such contact elements, and it has been found that a contact element made of a pressed and sintered or fired mixture of finely divided powders of graphitic material with a metal of high electrical conductivity,

such as copper, or silver, and sulphur or a metallic sulphide, provides a particularly desirable combination.

We have found that this type electrical brush contact element is preferably a block composed of carbonaceous material such as finely divided graphite, a metal such as finely divided silver, and a metallic sulphide such as silver sulphide. In some instances, the sulphide may be formed during the manufacturing process by adding powdered sulphur to a mixture of graphite and powdered metal, mixing, heating, and pressing the mixture together and thereby forming a metallic sulphide mixed with graphite and metal. In thus making a contact element, the carbonaceous material is mixed with the metallic powder and sulphur and is pressed in a mold at 10 to tons per square inch pressure and is then heated in a reducing atmosphere, such as hydrogen, at a temperature between 650 and 700 0. Another method of making this type contact element which has been found to be successful is to mix finely divided copper oxide, such as black copper oxide (CuO), with a finely divided carbonaceous material, such as graphite, to form a slurry with water, after which this mixture is heated While it is being mixed until it forms a dry powder. This mixture is then heated in a reducing atmosphere at a temperature between 600 and 900 C. to reduce the copper oxide, after which this powder is mixed with a finely powdered sulphur and pressed to the desired shape at a pressure of several tons per square inch and heated for several hours at a temperature between and 200 C. It is then fired in a reducing atmosphere for about four hours at a temperature between 700 and 750 C.

While we have described particular embodiments of our invention, modifications thereof will occur to those skilled in the art, and we desire it to be understood, therefore, that our invention is not to be limited to the particular arrangements disclosed, and we intend in the appended claims to cover all modifications which do not depart from the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. The method of making an electrical contact 50 element which comprises mixing finely-divided black copper oxide and finely-divided graphite with water to form a slurry, heating and agitat- REFERENCES CITED ing said slurry until it i converted t dry pow- The following references are of record in the der, heating the powder in a reducing atmosfile O this patenti phere at a temperature hetween 600 and 900 C. 5 UNITED STATES PATENTS to reduce the copper oxide, mixing the resultant product with a finely-divided sulphur powder, Number Name te pressing this mixture to the desired shape and 1,017,483 nt Feb. 13, 1912 heating the pressed product in a reducing atmos- 1,647,737 s Nov. 1, 1927 phere for about four hours at a temperature be- 10 1,899,064 t rey Feb. 28, 1933 tween 700 and 750 C. 2,148,133 Reuscher et a1 Feb. 21, 1939 ROY L ADAMS 2,267,372 Calkins et a1 Dec. 23, 1941 LYALL ZICKRICK. 

